Replacing dairy products with unfortified plant-based alternatives could reduce the intake of essential nutrients, according to a new study by the University of Surrey. Researchers found that even partial substitutions of milk, yoghurt and cheese with plant-based products could lower dietary levels of iodine, calcium, riboflavin and vitamin B12.
The study, conducted in collaboration with Queen’s University Belfast, highlights potential nutritional risks as more people adopt plant-based diets. Researchers suggest that mandatory fortification of plant-based alternatives and other foods, particularly bread, could help prevent deficiencies without compromising efforts to promote more sustainable diets.
Replacing Dairy Products Can Reduce Essential Nutrient Intake
Researchers analysed dietary data from more than 3,500 individuals aged between 18 months and 100 years. The information came from the UK’s National Diet and Nutrition Survey. Using a modelling technique, the team examined how replacing dairy products with commercially available plant-based alternatives could affect intake of four essential micronutrients: iodine, calcium, riboflavin and vitamin B12.
The findings showed that even relatively small reductions in dairy consumption could lead to noticeable declines in these nutrients. Iodine was particularly affected because most plant-based alternatives contain very little of it unless they are fortified.
Dr Katie Nicol, co-author of the study and Research Fellow at the University of Surrey, said:
“With the growing need to address environmental sustainability, many dietary recommendations are focused on plant-based diets and the reduced intake of animal products.
“With the rise in plant-based alternative foods, we need to know whether they are like-for-like replacements for the micronutrients that are found in dairy products. This is particularly important for vulnerable groups, including young children and adolescent females, who are more likely to be deficient in certain micronutrients, which could affect their overall health.”
The researchers found that replacing 20 to 35 per cent of dairy products with plant-based alternatives, under current market fortification levels, increased iodine inadequacy among adolescent females from 54 to 65 per cent. Among women aged 19 to 49, the figure rose from 32 to 42 per cent.
Complete replacement produced even greater shortfalls. Iodine inadequacy increased to 80 per cent among adolescent females and 72 per cent among adolescent males.
Iodine Deficiency Emerges as a Particular Concern
The study identified iodine as the nutrient most vulnerable to reduced dairy consumption. Iodine is essential for producing thyroid hormones, which regulate metabolism and support healthy growth and brain development. Adequate intake is particularly important during pregnancy, when the body’s iodine requirements increase.
Dr Sarah Bath, Associate Professor at the University of Surrey and lead author of the study, explained why the UK faces a particular risk.
“The UK is particularly vulnerable to iodine insufficiency due to a lack of an iodine fortification policy such as universal salt iodisation, which many other countries have.
“People may also be unaware of the importance of iodine, which is needed to make thyroid hormones to regulate our metabolism, support healthy growth and brain development. Iodine is particularly important during, pregnancy, when the requirement increases, but it is also essential prior to pregnancy to ensure that stores are optimised. People are also unaware that dairy products are a major source of iodine, particularly in the UK, and that plant-based alternatives, unless fortified, have a very low iodine content.”
The researchers highlighted adolescent females and women of reproductive age as groups that could be particularly vulnerable to inadequate iodine intake.
Food Fortification Could Help Prevent Nutritional Shortfalls
The team also investigated whether mandatory fortification of plant-based dairy alternatives could reduce the risk of nutrient deficiencies. The modelling showed that fortifying these products with essential micronutrients prevented declines in nutrient intake following dairy replacement.
However, iodine intake remained inadequate in 59 per cent of adolescent females, even after plant-based alternatives were fortified.
The researchers found that adding iodine-fortified bread to this strategy could further improve intake. This combination reduced iodine inadequacy among adolescent females to 37 per cent, making it the most effective approach examined in the study.
Dr Nicol emphasised the importance of balancing environmental goals with nutritional health.
“Nutrition policy must evolve in tandem with environmental targets however it is important that shifts towards more sustainable diets do not compromise on public health. Fortification of foods is one way that this could be achieved however government policy is needed to make this happen.”
Dr Anne Nugent from the School of Biological Sciences at Queen’s University Belfast also explained how the team developed its replacement scenarios:
“During the analysis, we first identified all foods and recipes containing dairy produce (milk, cheese and yogurt) in the national food survey for the UK, the National Diet and Nutrition Survey. Next, we conducted a series of replacement scenarios whereby we substituted the dairy present with an equal weight of plant based dairy alternatives. As the nutrient composition of dairy alternatives available on our supermarket shelves can vary, we also applied a condition to make sure that every dairy alternative we had identified in our previous market survey had an equal chance of selection. The last step was to examine the impact on dietary intakes of key nutrients following either the reduction or removal of dairy from the diet, replacing it with the dairy alternatives as above, and asking whether a series of fortification options could mitigate against any shortfalls in intake while avoid situations of excess.”
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